Percussive photoflash lamp and method of securing anvil thereof

ABSTRACT

A percussive-type photoflash lamp in which the primer anvil wire is secured coaxially within the primer tube by means of a plurality of conical indentations in the tube. The method of securing the anvil wire in this manner comprises: supporting the wire within the tube, simultaneously and uniformly pressing a plurality of radially disposed pins against the tube by means of one direction of motion of a cylinder having cam surfaces bearing against the pins, and then withdrawing the pins by reversing the direction of motion of the cylinder.

y pressing the tube by United States Patent [191 Pfetferle et a1.

[ Get. 16, 1973 METHOD OF SECURING ANVIL THEREOF Inventors: Donald H.Pfefferle; William C.

5 Primary Examiner--Charles W. Lanham Assistant Examiner-J. W. DavieFink, both of Montoursville, P [73 Assignee: Sylvania Electric Products,Inc.,

Attorney-Norman J. OMalley et a1. Danvers, Mass.

[57] ABSTRACT A percussive-type photoflash lamp in which the v. 22, 1971APP]. No; 201

22 Filed? Related U.S. Application Data [62] Division of Ser. No.89,653, Nov. 16, 1970.

within the tube, simultaneously and uniform] a plurality of radiallydisposed pins against [52] U.S. 29/517, 72/402, 431/93 [51] Int. B2ld39/04 [58] Field of Search...........,....... f f f d h means 0 onelI'CEtlOn O motion a Cy 111 Cf aVl cam surfaces bearing against thepins, and then withdrawing the pins by reversing the direction of motionof the cylinder.

10/1970 Anderson et al. 4 Claims 7 Drawing Figures u 4v 4 n PatentedOct. 16, 1973 2 Sheets-Sheet l PRIOR ART Patented Oct. 16, 19733,765,079

2 Sheets-Sheet 2 PERCUSSIVE PHOTOFLASH LAMP AND METHOD OF SECURING ANVILTHEREOF Thisis a division, of application Ser. No. 89,653, filed Nov.I6, 1970.

BACKGROUND OF THE INVENTION This invention relates to the manufacture ofphotoflash lamps and particularly those of the percussive type.

FIG. 1 shows a photoflash lamp having a primer suitable for: applicationof the present invention. The lamp comprises a length of glass tubingdefining an hermetically sealed lamp envelope 2 constricted at one endto define an exhaust tip 4 and shaped to define a seal 6 about primer 8at the other end thereof. The primer 8 comprises a metal tube 10, a wireanvil 12 and a charge of fulminating material 14. A combustible such asfilamentary zirconium 16 and a combustionsupporting gas such as oxygenare disposed within the lamp envelope.

Tube 10has a relatively thin wall, in the order of 3 mils, andpreferably is composed of an iron, nickel and chrome alloy. Prior toassembly, the tubing is heated in wet hydrogen at an elevatedtemperature to form a layer of chrome oxide on its surface, whichprovides an excellent interface for the hermetic glass-to-metal seal.The. wire anvil 12 is provided with a protuberance, or head, at the endthereof which is disposed within primertube 10 and protuberances, orlobes, 22 intermediate the ends thereof, with the body of fulminatingmaterial 14 located therebetween. Head 20 and lobes 22 aid instabilizing and supporting the wire anvil substantiallycoaxial withintheprimer tube 10 and in providing clearance between the fulminatingmaterial 14 and the inside wall of tube 10.

Operation of the lamp is initiated by an impact onto tube 10 to causedeflagration of the fulminating material 14 up through the tube toignite the combustible 16 I disposed withinthe lamp envelope.A'refractory bead 24, fused to the wire anvil 12 just above the innermouth of the primer tube It) eliminates burnthroughs and functions as adeflector to deflect and control the ejection of hot particles offulminating material from the primer tube.

The old method of firmly locating the anvil in the tubing wasaccomplished by providing a crimp26 in the metal tube, or or above thehead 20, by the use of crimping devices which consisted of three or foursections carrying curved jaws which when closed formed a circle; aroundthe tube. The diameter of the jaw circle was smaller than the o.d. ofthe tubing, and the jaws were mounted on pressure slides which forced20-mil thick jaws into the tubing wall. Frequent readjustment of thesejaws was necessary to prevent the formation of ears'28 on the tubing, asshown in FIG. 2. These ears 28 prevented the jawsfrom seating properlyon the tube when indenting the tube wall against the anvil. The shape ofthe forming jaws, which due to primer design can be only 15-25 milshigh, is frequently damaged by pressure and is also worm out by thehard, green chromeoxide formed on the surface of the tube. The cars inthe metal tubing frequently lead to a split in the thin tube wall alongthe sharp bend. This makes the lamp unusable as the contained oxygengas, which is under a pressure of 500-700 cm. Hg., will then escape. Theachieved rigidity of the anvil with respect to the inside wall of thestructure was also poor, and the frequency of loose anvils was nottolerable in the mass production of the percussive lamps.

The lobes, or heads, on the anvil which help to centralize the anvilwhich carries the fulminating material do not prevent the anvil fromfalling out of the metal tube when the lamp is turned upside down; theyonly prevent the fulminating material from rubbing against the wall whenthe charged anvil is dropped into the bulb and slides into the metaltubing. The fulminating material, when rubbing against the oxide-coveredin side wall of the tubing, frequently ignites and makes the ignitionsystem inoperative. The space between the inner wall surface of thetubing and the surface of the fulminating material is about 2 mils wide,and a very high degree of rigidity is necessary to arrive at areliability of +99.8 percent in lamp ignition, or less than 0.2 percentof inadvertent, premature firing.

SUMMARY OF THE INVENTION In view of the foregoing, a principal object ofthis invention is to provide a percussive-type photoflash lamp having aprimer structure which will withstand mechanical shock duringmanufacture, handling, and use without premature flashing.

Another object is to provide an improved method of securing a primeranvil wire within a primer tube of a percussive-type photoflash lamp. 7

These and other objects, advantages and features are attained, inaccordance with the principles of this invention, by providing aplurality of conical shaped indentations in the primer tube which bearagainst the wire anvil, the indentations being circumferentially spacedto firmly locate the anvil substantially coaxial with the tube. Themethod of so securing the anvil comprises: supporting the anvil wirewithin the tube; simultaneously and uniformly pressing a plurality ofradially disposed pins against the tube to provide the indentations; andthen withdrawing the pins.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will be more fullydescribed hereinafter in conjunction with the accompanying drawings, inwhich: i

FIg. 1 is an elevational view in section of a percussive-type photoflashlamp having a primer suitable for application of the invention and towhich previous reference has been made; I I I FIG. 2 is an enlargedscale, fragmentary elevation of the primer tube of thelamp of FIG. 1illustrating a faulty crimp applied by. prior art methods, also referredto earlier; I

FIG. 3 is an enlarged scale, fragmentary elevation in section of theprimer of FIG. 1 constructedin according with the invention;

FIG. 4 is an elevation view of the primer structure of FIG. 3illustrating the outer wall appearance of the primer tube;

FIG. 5 is a cross-section taken along the line 5-5 of FIG. 4;

FIG. 6 is a sectional elevation of a mechanism for indenting a primertube according to the invention; and

FIG. 7 is a diagram illustrating the lines of motion of the pinsemployed in the mechanism of FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENT In accordance with the presentinvention, the primer of the photoflash lamp of FIG. 1 includes, in lieuof the old type crimp 26, six conical shaped indentations 30 in tube 10(see FIGS. 3-5) which are circumferentially spaced and bear against wireanvil 12 to precisely locate and firmly retain the anvil in the desiredcoaxial position within the primer tube. More specifically, as shown inthe sectional view of FIG. 3, the charged anvil is anchored coaxiallywithin the primer tube by virtue of the tube indentations 30 firmlycontacting anvil 12 below the body of fulminating material 14 and abovethe protuberance, or head, 20. As best shown in the primer elevation ofFIG. 4 and the cross-section of FIG. 5, the six indentations 30 areequally spaced about tube 10 in a plane perpendicular to thelongitudinal axis of the tube.

The method of providing the improved anvil retaining configuration ofFIGS. 3-5 according to the invention comprises: (1) supporting the anvilwire 12 in a substantially coaxial position within tube 10; (2) applyingto the outer wall of tube 10 the uniform indenting pressure of sixconically pointed pins which are radially disposed about tube 10 toconverge toward the longitudinal axis thereof; (3) and then withdrawingthe pins from the tube.

FIG. 6 shows a simple mechanical arrangement for driving pins 32symmetrically against the longitudinal axis of primer tube 10. Two ofthe pins 32 are shown an instant after producing the indentations 30 intube 10. The mechanism includes a cylindrical stationary member 36having six radial bores 38 in the horizontal plane for supporting thepins 32 and a vertical bore 40 for receiving the primer tube 10 of apartially completed photoflash lamp 34. The bottom of the vertical boresupports the primer tube 10 at the proper vertical position with respectto pins 32. The mechanism also includes a movable cylinder 44 whichcoaxially surrounds member 36.and has a set of cam surfaces 46 and 47which retain cam follower heads 48 at the outer ends of pins 32.Cylinder 44 also includes slots 50 through which the pins 32 pass andwhich permit longitudinal motion of the cylinder. As illustrated in FIG.6, cylinder 44 may comprise an assembly of two tapered, annular memberswhich are bolted or riveted together.

Preferably, pins 32, are made of a conically shaped rod of carballoy, aTungsten carbide alloy, and carry a rounded pressure head 48 of hardenedsteel for bearing against cam surfaces 46 and 47. The configuration ofthe mehcanism in such that the pins are disposed in a planeperpendicular to the longitudinal axis of tube 10 and arranged toconform to the radii of a six cornered polygon. The use of relativelyheavy pins made from "carballoy" and ground to a precision pointcontributes substantially toward maintaining the critical tolerances ofthe lower part of the primer, which typically are about 120.5 to $1.0mil.

Outer cylinder 44, which is coaxial with the primer tube 10 of lamp 34,operates by a longitudinal, up and down motion, as indicated by thearrows. The cam surfaces 46 and 47 are shaped to move all pinssimultaneously in and out, as indicated in FIG. 7. FIG. 6, showscylinder 44 in a position whereby all pins are pressed into tube 10; thepins are then withdrawn by reversing the direction of longitudinalmotion of the cylinder. In summary, an improved percussive-typephotoflash lamp is provided by having the primer structure secured bythe simultaneous indentation of conically pointed pins to obtain preciselocation and firm retention of the anvil. The location of the body offulminating material at about 1 to 2 mils distance from the wall ismaintained on high speed production machinery assuring a +99.8 percentflashability of the lamp, which means that during all production stepsthe fulminating material is not deflagrated by mechanical shock. Theadvantages of the improved strjcture is particularly evident when lampsare subjected to a drop test, in which the entire flash assembly isdropped from 4, 5, or 6 feet onto a concrete floor. Only 0.1 percent to0.3 percent of the improved lamps flash by this rather severe testingmethod, whereas lamps made by circular crimping jaws exhibited to 30percent ignition in the above drop test.

What we claim is:

1. The method of securing a primer anvil wire within a primer tube of apercussive-type photoflash lamp, said method comprising:

supporting said primer tube at a predetermined vertical position withrespect to a plurality of conically pointed pins radially disposed aboutsaid tube in a symmetrical pattern about the longitudinal axis thereof;

supporting said anvil wire within said tube substantially coaxialtherewith;

pressing said plurality of pins simultaneously and uniformly againstsaid tube toward the longitudinal axis thereby by one direction oflongitudinal motion of a cylinder which is coaxial with said tube andhas a set of cam surfaces retaining and bearing against follower headsat the outer ends of said pins, the pressure applied to said pins beingsufficient to securely retain said anvil concentrically within said tubeby means of the resulting indentations made in said tube;

and withdrawing said pins from said tube by reversing the direction oflongitudinal motion of said cylinder whereby said set of cam surfacesbear on said follower heads in a manner causing said pins to be pulledradially outward by said cam surfaces.

2. The method of claim 1 in which said pins are shaped from a rod oftungsten carbide alloy.

3. The method of claim 1 in which said pins are disposed in a planeperpendicular to the longitudinal axis of said tube and arranged toconform to the radii of a polygon.

4. The method of claim 3 in which at least six of said pins areemployed.

1. oThe method of securing a primer anvil wire within a primer tube of a percussive-type photoflash lamp, said method comprising: supporting said primer tube at a predetermined vertical position with respect to a plurality of conically pointed pins radially disposed about said tube in a symmetrical pattern about the longitudinal axis thereof; supporting said anvil wire within said tube substantially coaxial therewith; pressing said plurality of pins simultaneously and uniformly against said tube toward the longitudinal axis thereof by one direction of longitudinal motion of a cylinder which is coaxial with said tube and has a set of cam surfaces retaining and bearing against follower heads at the outer ends of said pins, the pressure applied to said pins being sufficient to securely retain said anvil concentrically within said tube by means of the resulting indentations made in said tube; and withdrawing said pins from said tube by reversing the direction of longitudinal motion of said cylinder whereby said set of cam surfaces bear on said follower heads in a manner causing said pins to be pulled radially outward by said cam surfaces.
 2. The method of claim 1 in which said pins are shaped from a rod of tungsten carbide alloy.
 3. The method of claim 1 in which said pins are disposed in a plane perpendicular to the longitudinal axis of said tube and arranged to conform to the radii of a polygon.
 4. The method of claim 3 in which at least six of said pins are employed. 